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Seabird-induced natural mortality of forage fish varies with fish abundance : evidence from five ecosystems
No full textForage fish populations often undergo large and rapid fluctuations in abundance. However, most of their predators are buffered against such fluctuations owing to their slower pace of life, which allows them to maintain more stable populations, at least during short periods of food scarcity. In this study, we investigated top-down processes exerted by seabirds on forage fish stocks in five contrasted marine ecosystems, compiling numerous data sets on seabird counts, diets, energetic needs and prey energy content and abundance. Off Norway, South Africa, Peru, Sweden and Scotland, we found that predation pressure-estimated as the proportion of a fish stock consumed by seabirds-was generally low (median = 1%), but increased sharply at low levels of prey abundance. When prey biomass decreased below 15-18% of its maximum recorded value, predation by seabirds became a source of important additional pressure on prey stocks (similar to 20% of prey biomass is consumed by seabirds). An earlier empirical study advocated for keeping forage stocks from falling below a threshold of 33% of long-term maximum prey biomass in order to safeguard seabird breeding success, but here we further suggest that a threshold of 18% should be considered as a limit not to be exceeded for the sake of the forage fish themselves, and below which extra cautious management of fisheries may be required. Nevertheless, despite exceptionally high rates of predation on some occasions, predation pressure was not correlated with prey dynamics, suggesting an absence of prey entrapment due to seabirds alone in these five ecosystems
Taxonogenomics description of Bacillus dakarensis sp. nov., Bacillus sinesaloumensis sp. nov. and Bacillus massiliogabonensis sp. nov., three new species isolated from human stools
No full textUsing microbial culturomics, three Bacillus strains were isolated, identified and characterized following the taxonogenomics strategy. Bacillus dakarensis strain Marseille-P3515(T) (=CSURP3515), Bacillus sinesaloumensis strain Marseille-P3516(T) (=CSURP3516), and Bacillus massiliogabonensis strain Marseille-P2639(T) (=CSURP2639) were isolated from human stool samples. The phylogenetic analysis, phenotypic characteristics and genotypic data presented here prove that these three bacteria are different from previously known bacterial species with standing in nomenclature and represent new Bacillus species
Acoustic probing of the particle concentration in turbulent granular suspensions in air
No full textDilute gas-particle suspensions in which the particles are carried by the fluid are found in various industrial and geophysical contexts. One fundamental issue that limits our understanding of such systems is the difficulty to obtain information on the particle concentration inside these often optically opaque suspensions. To overcome this difficulty, we develop ultrasonic spectroscopy to monitor the local particle concentration phi of glass particles (with diameters d similar to 77 mu m or 155 mu m) suspended in air. First, we determine the minimal air velocity, U, necessary to suspend the particles from the maximum decrease in the transmitted wave amplitude and velocity of ultrasound propagating through the suspension. Next, setting the air velocity at U, we increase the mass of particles and monitor acoustically the local solid volume fraction, phi, by measuring the ultrasound wave attenuation coefficient and phase velocity as a function of frequency on the basis of classical scattering and hydrodynamic models. For the frequency ranges and suspensions considered here, the viscous dissipation dominates over scattering and thermal conduction losses. We show that, for a characteristic air velocity U, the locally measured phi reaches a critical value, in agreement with a recent study on turbulent gas-particle mixtures. Moreover, we find that this critical phi increases with the size of the particles. Finally, analysis of the temporal fluctuations of the locally measured solid volume fraction, suggests that high density regions (clusters) are present even in suspensions with concentrations below the critical concentration. This differs from the current hypothesis according to which the critical concentration coincides with the onset of cluster formation
Physical limitation of pesticides (chlordecone) decontamination in volcanic soils : fractal approach and numerical simulation
No full textIn the French West Indies, the chlordecone (organochloride pesticide) pollution is now diffuse becoming new contamination source for crops and environment (water, trophic chain). Decontamination by bioremediation and chemical degradation are still under development but the physical limitations of these approaches are generally not taken into account. These physical limitations are related to the poor physical accessibility to the pesticides in soils because of the peculiar structural properties of the contaminated clays (pore volume, transport properties, permeability, and diffusion). Some volcanic soils (andosols), which represent the half of the contaminated soils in Martinique, contain nanoclay (allophane) with a unique structure and porous properties. Andosols are characterized by pore size distribution in the mesoporous range, a high specific surface area, a large pore volume, and a fractal structure. Our hypothesis is that the clay microstructure characteristics are crucial physico-chemical factors strongly limiting the remediation of the pesticide. Our results show that allophane microstructure (small pore size, hierarchical microstructure, and tortuosity) favors accumulation of chlordecone, in andosols. Moreover, the clay microporosity limits the accessibility of microorganisms and chemical species able to decontaminate because of poor transport properties (permeability and diffusion). We model the transport properties by two approaches: (1) we use a numerical model to simulate the structure of allophane aggregates. The algorithm is based on a cluster-cluster aggregation model. From the simulated data, we derived the pore volume, specific surface area, tortuosity, permeability, and diffusion. We show that transport properties strongly decrease because of the presence of allophane. (2) The fractal approach. We characterize the fractal features (size of the fractal aggregate, fractal dimension, tortuosity inside allophane aggregates) and we calculate that transport properties decrease of several order ranges inside the clay aggregates. These poor transport properties are important parameters to explain the poor accessibility to pollutants in volcanic soils and should be taken into account by future decontamination process. We conclude that for andosols, this inaccessibility could render inefficient some of the methods proposed in the literature
Health care access among underserved groups
No full textA component of the performance-based financing intervention implemented in Burkina Faso was to provide free access to healthcare via the distribution of user fee exemption cards to previously identified ultra-poor. This study examines the factors that led to the receipt of user fee exemption cards, and the effect of card possession on the utilisation of healthcare services. Methods: A panel data set of 1652 randomly selected ultra-poor individuals was used. Logistic regression was applied on the end line data to identify factors associated with the receipt of user fee exemption cards. Random-effects modelling was applied to the panel data to determine the effect of the card possession on healthcare service utilisation among those who reported an illness six months before the surveys. Results: Out of the ultra-poor surveyed in 2017, 75.51% received exemption cards. Basic literacy (p = 0.03), living within 5 km from a healthcare centre (p = 0.02) and being resident in Diébougou or Gourcy (p = 0.00) were positively associated with card possession. Card possession did not increase health service utilisation (ß = -0.07; 95% CI = -0.45; 0.32; p = 0.73). Conclusion: A better intervention design and implementation is required. Complementing demand-side strategies could guide the ultra-poor in overcoming all barriers to healthcare access
Maroc : la bi-citoyenneté à l'épreuve du confinement
No full textLe déconfinement progressif en cours laisse entrevoir les traces laissées par la gestion de la 'crise du coronavirus'. Ce dernier apparaît comme un révélateur - au sens photographique - de la condition transnationale aujourd'hui. Il en montre des aspects auparavant invisibles ou latents, à travers la ' solution ' que représente le confinement. Les situations qu'il implique et les actes engendrés en conséquence donnent à voir crûment les contours de l'entre-deux, de l'hybridité, et de la double appartenance
